The present invention relates generally to the field of gimbal type devices and to the field of devices for providing two orthogonal degrees of freedom to a load device. More particularly, the present invention is related to the field of servo controlled, rate stabilizing platforms for sensor systems which are particularly suitable for use for guidance systems such as missile guidance systems and surveillance systems for data/intelligence gathering and target tracking. While the present invention is particularly suitable for such applications, the present invention relates more generally to the field of positioning systems and may be utilized anywhere that an object or device requires orientation and repositioning from one position to another.
Traditionally, stabilized sensor platforms have been very high cost systems due to the fact that they are intricate and complex mechanical structures. Stabilized missile sensors require at least two degrees of freedom of movement (azimuth and elevation). These two degrees of freedom of movement have been accomplished in the past by an inner/outer gimbal arrangement of the stabilized platform. In an improved arrangement as is shown, for instance, in U.S. Pat. No. 4,324,378 the inner gimbal torque motor is secured to the outer gimbal ring to permit increased weight and volume sensors to be packaged and located at the center of rotation of the gimbal axis. A problem with the gimbal arrangement disclosed in the aforementioned patent is that the nodal point of an antenna system mounted on the platform cannot be positioned at the center of the axis of rotation of the antenna system due to the fact that the center of rotation of the gimbal is located in a space occupied by the platform. Further, the platform is driven by a gear arrangement which must be affixed to the platform itself thereby further precluding positioning of the antenna nodal point at the center of the axis of rotation.
Another positioning device useable for positioning an antenna or other bore-cited device in azimuth and elevation is disclosed in U.S. Pat. No. 3,215,391. The device disclosed in that patent requires utilization of U-joints in the extendable supports in order to achieve spherical rotation capability of the platform. This type of arrangement suffers from inherent instability. For this reason such devices are not acceptable for utilization in many applications such as missile guidance.
Other prior art gimbal designs suffer from lack of space requirements for electronics and hardware within the platform and also lack of symmetry about the rotation axes.